How to efficiently store electricity generated by solar energy

Nowadays, solar energy is already a well-known and respected clean energy source. As for how to store the electricity generated by solar energy, it may not be fully popularized at the public level. Solar power panels and batteries need to be well coordinated in order to more efficiently allow sufficient electrical energy to continue to "shine and heat" during periods when there is no sunlight. Even if the power generation efficiency of the solar panels is very high, if the capacity of the battery is not enough, then There may also be insufficient power at night.

Taking the more common off-grid home configuration as an example, an independent solar power generation system consists of solar panels, solar controllers, and batteries (packs); if the output power supply is AC 220V or 110V, an inverter is also required. Solar panels can generate electricity for a limited time and do not work all day long. When the sun is bright and sunny, the effective power generation time in a day is about 5-6 hours. If the generated electricity cannot be stored, then the solar power generation efficiency will be wasted no matter how high it is. Therefore, in off-grid power generation systems, batteries that store electrical energy play an important role.

The battery is an indispensable energy storage component of the off-grid photovoltaic power generation system. Its main function is to store the electrical energy of the solar power generation system and provide power to the load when the amount of sunlight is insufficient, at night and in emergency situations.

Currently, the batteries commonly used in off-grid photovoltaic power generation systems are electrochemical energy storage, which uses chemical elements as energy storage media, mainly including lead-acid batteries, flow batteries, sodium-sulfur batteries, lithium-ion batteries, etc. Currently, the main applications are lithium batteries and lead-acid batteries.

Lead-acid batteries

Lead-acid battery is a battery whose electrodes are mainly made of lead and its oxides, and the electrolyte is sulfuric acid solution. Because the internal resistance of the battery is small, it can cope with the discharge needs of large currents, so its application scope is mainly UPS uninterruptible power supply. , control switches, alarms, automobile traction power supplies, electric bicycles, etc., those with higher capacity density are mainly used in communication backup power supplies for large base stations. Lead-acid batteries have simple components, mature regeneration technology, and high recycling value. They are the easiest batteries to recycle. But its disadvantages are heavy weight, limited battery capacity, and short life. Lead-acid batteries generally have a lifespan of about two years within 500 deep charges and deep discharges.

Lithium Ion Battery

Lithium-ion batteries are composed of four parts: positive electrode material, negative electrode material, separator and electrolyte. According to the different materials used, they are mainly divided into four types: lithium cobalt oxide, lithium manganate, ternary lithium, and lithium iron phosphate. Because ternary lithium and lithium iron phosphate batteries are currently widely used in various industries, a more detailed introduction will be given next to these two lithium batteries.

The nickel in the ternary lithium battery can increase the reversible capacity of the material and increase the energy density of the battery, which also increases the battery capacity; cobalt can improve the ability of lithium ions to deintercalate and increase the charging and discharging speed of the battery, which can increase the Charging efficiency; the role of manganese or aluminum is mainly to improve the safety and stability of the battery. Therefore, the combination of the three materials can greatly increase the energy density of the battery, and the battery of the same volume can have a higher capacity. Lithium iron phosphate battery, the full name of lithium iron phosphate lithium-ion battery, uses lithium iron phosphate (LFP for short) as the cathode material. It is the safest lithium-ion battery cathode material among several battery materials, and carbon is used as the negative electrode material. .

Ternary lithium batteries and lithium iron phosphate batteries each have their own advantages and disadvantages, and they have a very high share in the battery market. Data from the China Automotive Power Battery Industry Innovation Alliance shows that in the first 10 months of 2021, the cumulative installed capacity of power batteries in my country reached 107.5GWh, of which the installed capacity of ternary batteries and lithium iron phosphate batteries accounted for 99.9% of the total installed capacity. 8%. Compared with lithium iron phosphate batteries, ternary lithium batteries have a higher capacity density in the same volume, which can store more power, which means longer battery life. They are widely used in new energy vehicles; however, due to the The high-temperature structure of nickel-cobalt-aluminum, the main cathode material of lithium-ion batteries, is unstable, resulting in poor battery safety at high temperatures, and too high a pH value can easily cause the monomer to bloat, which may cause danger.

In comparison, lithium iron phosphate has better thermal stability. One reason is that the P-O bond in the lithium iron phosphate crystal is stable and difficult to decompose. Even at high temperatures or overcharge, the structure will not collapse like lithium cobalt oxide. It generates heat or forms strong oxidizing substances, so it has good safety. Lithium iron phosphate batteries have moderate operating voltage, high discharge power, fast charging, long cycle life, and higher stability in high temperature and high-heat environments. As the advantages of lithium iron phosphate batteries are gradually being valued, the products are widely used in electric new energy vehicles, energy storage fields, small computer rooms, weak current rooms and other indoor distribution (English abbreviation IBS, Indoor Building Solution) systems, new energy outdoor sites, communications Base stations, indoor and outdoor non-air-conditioned sites, unmanned sites such as radio and television, military, petroleum and meteorology, etc.

The demand for lithium iron phosphate battery materials has also seen a sharp increase in recent years. According to data from the Gaogong Industrial Research Lithium Battery Institute (GGII), China's lithium iron phosphate cathode material shipments in 2021 will be 470,000 tons, a year-on-year increase of 277%. According to the analysis of the Lithium Battery Research Institute of Gaogong Industrial Research Institute, one of the important reasons for the substantial growth in material shipments is that the low-temperature performance of lithium iron phosphate batteries continues to improve with year-by-year research and improvements. Advances in lithium iron phosphate battery technology and thermal management The advancement of the system has also helped improve the low-temperature endurance of models equipped with lithium iron phosphate batteries, and due to the sharp increase in the price of upstream raw materials, the pressure on car companies and power battery companies to reduce costs has increased. Lithium batteries are a more cost-effective option.

Lithium iron phosphate battery, what else is better?Extra long battery life

In terms of battery life, for the lead-acid batteries mentioned above, the cycle life of long-life lead-acid batteries is about 300 times, and the highest is only 500 times, while the cycle life of lithium iron phosphate power batteries can reach more than 2,000 times. Standard charging (5 hours rate) use, can reach 2000 times. Lead-acid batteries of the same quality last "half a year for new ones, half a year for old ones, and another half year for maintenance", which is only 1 to 1.5 years at most. When used under the same conditions, the theoretical life of lithium iron phosphate batteries will reach 7 to 8 years. Comprehensive consideration, the performance-price ratio is theoretically more than 4 times that of lead-acid batteries. High-current discharge can quickly discharge at a high current of 2C. Under a special charger, the battery can be fully charged within 40 minutes at 0.8C, and the starting current can reach 2C. Lead-acid batteries do not have this performance.

Non-toxic and environmentally friendly

Lithium iron phosphate batteries are generally considered to be free of any heavy metals and rare metals (nickel metal hydride batteries require rare metals). They are non-toxic and non-polluting through SGS certification, comply with European RoHS regulations, and have the authoritative "Green Battery Certificate". One of the important reasons why lithium batteries are favored by the industry is due to environmental protection considerations. Therefore, the lithium battery industry chain project has been included in the "863" national high-tech development plan during my country's "Tenth Five-Year Plan" period and has become a key national support and Projects that encourage development.

Charge and use anytime (memory effect)

If the battery is a nickel-cadmium battery, due to the memory of nickel-metal hydride and nickel-cadmium batteries, if they are not fully charged and discharged for a long time, and often work under the condition of being fully charged but not fully discharged, it is easy to leave traces in the battery, and the capacity will quickly fall below the rated value. Capacity value, this phenomenon is called battery memory effect. If the battery memorizes the user's daily charging and discharging range and pattern, it will be difficult to change this pattern over time, and it will no longer be able to charge or discharge to a large extent. Lithium iron phosphate batteries do not have this effect. No matter what state the battery is in, it can be charged and used at any time. There is no need to discharge it first and then charge it.

Small size, light weight, large capacity

Generally, lead-acid battery packs weigh 16-30 kilograms and are relatively large. The volume of a lithium iron phosphate battery with the same specification and capacity is 2/3 of the volume and 1/3 of the weight of a lead-acid battery. Taking a 12V/65AH lead-acid battery as an example, the weight is about 18.5 kg. A lithium battery as an example, taking a 12.8V/63AH unit, weighs about 4.4 kg. With lighter weight and smaller volume, lithium batteries have more advantages than ordinary ones. Batteries (lead-acid, etc.) have larger capacity.

Lithium iron phosphate battery application: Zhenghao 48V full-scenario power supply systemCurrent solar panels generally have a long service life, and the durability and safety of the battery must naturally keep up. The quality of the battery will directly affect the reliability of the entire system. Recently, Zhenghao EcoFlow's newly launched 48V full-scenario power system uses 48V vehicle-grade lithium iron phosphate batteries to form the battery pack of the power system. A single battery has battery specifications of 2 kilowatt hours and 5 kilowatt hours for users to freely choose. , can be stacked up to 15 kilowatt-hours of electricity, allowing users to not worry about power, go off-grid with confidence, and enjoy off-grid life. In traditional power systems, the battery needs to be reserved in advance according to the power level, and it is difficult to disassemble or install later. Zhenghao 48V full-scenario power system is designed with power modules that can be stacked vertically. In the case of limited space, the upward stacking method can greatly Save space, the stacking method can be flexibly adjusted according to the actual situation of the space, and it is easy to disassemble. Zhenghao's 48V full-scenario power supply system maximizes the advantages of lithium iron phosphate in the off-grid power supply system category.